Nerve palsies Flashcards
What is the primary function of the oculomotor nerve (CN III)?
Supplies all extraocular muscles except the superior oblique (CN IV) and the lateral rectus (CN VI)
The oculomotor nerve is crucial for eye movement and function.
What is the typical presentation of oculomotor nerve palsy?
‘Down and out’ appearance of the affected eye
This occurs due to unopposed action of lateral rectus and superior oblique muscles.
What additional symptoms can occur with oculomotor nerve palsy?
Ptosis and mydriasis
Ptosis is due to loss of innervation to levator palpebrae superioris and mydriasis results from loss of parasympathetic fibers.
Which muscle does the trochlear nerve (CN IV) innervate?
Superior oblique muscle
The trochlear nerve is responsible for downward eye movement.
What is a common symptom of trochlear nerve palsy?
Vertical diplopia when looking inferiorly
This occurs due to loss of the superior oblique’s action.
How do patients with trochlear nerve palsy often compensate for their symptoms?
They tilt their head forwards and tuck their chin in
This head position minimizes vertical diplopia.
What is torsional diplopia, and which nerve palsy is associated with it?
Torsional diplopia is caused by trochlear nerve palsy
It occurs as the superior oblique assists with eye intorsion.
What muscle does the abducens nerve (CN VI) innervate?
Lateral rectus muscle
The abducens nerve controls lateral eye movement.
What does abducens nerve palsy result in?
Unopposed adduction of the eye, causing a convergent squint
This leads to horizontal diplopia, worsening when looking towards the affected side.
What characterizes facial nerve palsy?
Unilateral weakness of the muscles of facial expression
It can result from both upper and lower motor neuron lesions.
What is the most common cause of lower motor neuron facial palsy?
Bell’s palsy
This results in weakness of all ipsilateral facial muscles.
How does upper motor neuron facial palsy differ from lower motor neuron facial palsy?
Upper motor neuron facial palsy spares the upper facial muscles
This is due to bilateral cortical representation.
What is the most common cause of upper motor neuron facial palsy?
Stroke
Stroke can lead to unilateral facial muscle weakness.
